The present invention relates to a housing for an optical measurement device, e.g., for yarn monitoring, and more particularly to such a housing being produced from a plastics material by prototyping and receiving components of the measurement device such as the light source, sensor or lens. As used herein, the term “prototyping” refers specifically to a manufacturing methodology by which an amorphous body of material is formed into a solid object, e.g., via injection molding, according to the “Urformen” definition established by German DIN (Deutsches Institut für Normung, i.e., the German Institute for Standardization) Standard 8580. The present invention further relates to a method for producing a housing of an optical measurement device.
German Patent Publication DE 101 50 581 A1 describes a housing for a yarn sensor, which is produced from plastics material by the injection molding method and is used to receive electronic components of the yarn sensor. The housing has a measurement device with a measuring gap, through which a yarn is guided during the measurement. The measurement device comprises an optical sensor and a light source, which are enclosed in the measurement device and are arranged on the sides of the measuring gap facing the yarn. The surfaces of the measurement device become soiled while the yarn is being guided through as a result of finish adhering to the yarn or because of fibers or dust, which leads to an impairment of the measurement results. The required cleaning of the surfaces is problematical as with improper use of aggressive cleaners or by means of mechanical loading during cleaning, the surfaces of the measurement device may be directly damaged.
An optical measurement device for detecting discontinuous defects in a textile woven fabric is known from U.S. Pat. No. 4,728,800, in which the measurement device is arranged behind a glass panel for protection. The device comprises a housing which is used to receive optical components of a detector system. The textile woven fabric to be monitored is guided past the glass panel. The glass panel prevents the penetration of dust and other foreign bodies into the interior of the housing so that the function of the optical components of the measurement device is retained. The glass panel is received in a groove on one side of the housing and sealed with respect to the housing by a suitable seal and thus mounted in the groove by means of the sealing material.
The gluing of such glass panels to the housing by means of an adhesive is also known from the prior art. The aim of this gluing is also to prevent the penetration of dust or other foreign bodies through gaps produced because of joining tolerances which occur between the housing and the glass panel, into the measurement device, and also to produce mechanical strength to prevent the glass panel falling out.
These methods known from the prior art for attaching glass panels to the housing of the optical measurement device are not, however, able to eliminate or avoid a series of undesired influences. Thus, the adhesive used to glue the glass panels tends to be attacked or decomposed by cleaning agents which are used for the required regular cleaning of the glass panels. This can lead to the glass panels no longer being adequately secured against falling out.
This equally applies to the sealing material used according to U.S. Pat. No. 4,728,800. Moreover, at the edges of the glass panel projecting over the housing, fibers may accumulate on the adhesive or on the sealing material. This leads to the functionality of the measurement device being impaired because of the soiling from the fibers or dust, in particular if the measurement device is configured to carry out the detection of reflected light and the detection of shading.